As set forth in some detail in U.S. Pat. No. 4,216,657, assigned to the assignee of the present invention, the difference in temperature between the surface waters and the subsurface waters in certain oceans and lakes, for example, may be harnessed to produce electrical energy by providing a large floating structure which is evacuated and which draws warm water from the surface of the ocean at a temperature of perhaps 20 or 25 degrees Centigrade, and cold water (5 degrees Centigrade) from a few hundred meters below the surface of the ocean. The warm water is initially directed from a point near the surface of the ocean to a hydraulic electric generator located toward the bottom of the floating structure perhaps 100 to 150 meters below the surface of the ocean. The warm water is then sprayed upward into the bottom of an evacuated chamber, with the spray nozzle plate being designed to produce small uniform evenly spaced droplets. Evaporation or boiling from the surface of the droplets produces a large volume of water vapor which rises rapidly toward the top of the chamber, sweeping the droplets with it. The top of the vessel connects to a spray condenser fed by cold sea water pumped up to the top of the chamber, with the cold water being taken from below the thermocline, perhaps 300 or more meters below the surface of the ocean.
Experimental tests indicated that the mist flow process operated satisfactorily. However, the size of the required floating reinforced concrete structure would have been larger than desirable, with the continuous funnel shaped expansion of the cross section of the unit from bottom to top. In addition, the need for providing equipment to pump the cold water to the top of the structure increased the cost of the structure substantially.
Accordingly, objects of the present invention include reducing the size and the cost, and increasing the efficiency of mist flow type thermal energy converters.